I'm working on a equipment room with a lot of racks and two panels that feed them. Is their a magical inductive tool that I can put on the panel next to a specific breaker and which has a test lead that I can plug into an outlet at the rack? Its against regulations to enter a panel.
This style of tracer has a "auto gain feature" that remembers the last highest gain and will only beep on an equal or higher signal. I'm not sure who makes this tracer, it seems to be sold under Klein and Amprobe labels, just different colors. The signal injector also seems to also have different voltage ratings.
Do others find that these types of products ACTUALLY work? I used them years ago and found that at best they worked 50% of the time. I haven't used them since.
Sometimes distance can be a factor. The tester Larry fine pointed to is rarely effective at distances over 150 feet. I have found the Greenlee CS 8000 to be effective at distances up to 500 feet, this tracer also is the auto gain type.
While I have not had first hand experience with this make:
https://www.tasco-usa.com/ I've people tell me it is very good. Anyone have any experience with this company?
It's very accurate at short distances, but might present a problem for the OP because you need to open the panel while powered up.
Depending on the type and quantity of equipment in the racks, there may be a lot of RFI/EMI in the room with RF noise also riding on the power circuits.
Some of these "fox and hound" sensors are fooled by EMI/RFI. So I would not count on them 100% but they are certainly good as a starting point.
Switch mode power supplies ( modern computer power supplies) make a noise that makes it difficult to discern on some types of circuit detectors, one example of this type would be an Amprobe AT 1000, this type of tracer shows or displays the switch mode noise as well as the signal injector "noise". It's up to the operator to determine if the signal is from a power supply or from the injector.
Are these tools trust worthy? Greenlee and Klein make them. It may be the skill of the operator. I never have much luck with stud detectors, for instance, but that's my inexperience in using them.
I had a GB (Garder-Bender) breaker finder years ago and it was a piece of crap. I think it worked correctly maybe twice in hundredths of attempts. Fast forward a few years and I tried an Ideal. I was/am very pleased with it. I would give it a 95% success rate.
The thing you have to do and keep in mind, is that you have to scan the panel at least twice for it to learn the circuits. I usually do it three times for my own satisfaction.
What I mean by scan is to run it slowly down the breakers on each side. On the first (and sometimes the 2nd) pass it will indicate on several breakers. After you have done this two or more times it most usually will narrow it down to the one breaker you are looking for.
Little Bill's comment on going around twice is vital if you are using one of the "auto gain" types.
The Greenlee CS8000 also has a feature that displays if the signal injector is powered up or if it's injecting into a dead circuit, not fool proof, but goes a long way to determining if you have the correct circuit breaker. It's also ten times the price, or more than the one Larry fine pointed to.
I work at a 24/7/365 facility that was built in stages over a 40 year period. We have over 150 circuit breaker panels that are also installed over the same time period, most without accurate schedules. Many of the original panels had circuits over 1000 feet away and the newer panels may overlap the coverage of the original panels. I'm under similar restrictions as Installer has, although my restrictions are based on arcflash ratings. Many of our panels have arcflash ratings that are above 40 cal, so they cannot be accessed while under power period. However the 480 side of the transformer can be accessed due to better coordination. When we run into a situation where we cannot determine which panel the circuit comes from we often use a box we made with a repeat cycle timer and a contactor, which we add a load an cycle the load on and off. Most times we can use an ammeter to "see" the load cycle on and off on the 480 side of the transformer. At this point we know that we have the right panel, and continue the "detective work"
I mean, this may be one of those cases where you need to work with someone who has experience with them and can mentor you on the tips and tricks. 
